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Abstract:

Embodiments of devices, methods, and non-transitory computer readable
media for monitoring a subject are presented. The monitoring device
includes at least one sensor configured to monitor one or more
physiological parameters of a subject and a processing unit operatively
coupled to the sensor. The sensor comprises a plurality of radiation
sources and detectors disposed on a flexible substrate in a designated
physical arrangement. The processing unit is configured to dynamically
configure an operational geometry of the sensor by controlling the
intensity of one or more of the radiation sources and the gain of one or
more of the detectors so as to satisfy at least one quality metric
associated with one or more physiological parameters of the subject.

Claims:

1. A monitoring device, comprising: at least one sensor configured to
monitor one or more physiological parameters of a subject, wherein the
sensor comprises a plurality of radiation sources and detectors disposed
on a flexible substrate in a designated physical arrangement; a
processing unit operatively coupled to the sensor, herein the processing
unit is configured to dynamically configure an operational geometry of
the sensor by controlling the intensity of one or more of the radiation
sources and the gain of one or more of the detectors so as to satisfy at
least one quality metric associated with one or more physiological
parameters of the subject.

2. The monitoring device of claim 1, wherein the operational geometry of
the sensor comprises a subset of one or more radiation sources and
detectors selected from the plurality of radiation sources and detectors
disposed on the flexible substrate, which when operational, provide
desired location and intensity characteristics.

5. The monitoring device of claim 1, wherein the plurality of radiation
sources and detectors are disposed on the flexible substrate using a
roll-to-roll assembly technique.

6. The monitoring device of claim 1, wherein the substrate is a flexible
polyimide substrate.

7. The monitoring device of claim 1, wherein the sensor comprises a
pixellated optical transducer comprising the plurality of radiation
sources and detectors arranged in an array on the flexible substrate.

8. The monitoring device of claim 1, wherein the radiation sources are
disposed on the flexible substrate at a plurality of distances from the
detectors to allow different depths of light penetration into a region of
interest of the subject.

9. The monitoring device of claim 1, wherein the radiation sources
comprise sources configured to generate radiation at a plurality of
wavelengths.

10. The monitoring device of claim 9, wherein the radiation sources
comprise one or more light emitting diodes, one or more organic light
emitting diodes, one or more laser diodes, or combinations thereof.

12. The monitoring device of claim 1, wherein a response curve of the
detectors covers a spectrum band of interest.

13. The monitoring device of claim 1, wherein the quality metric
comprises signal-to-noise ratio, an amplitude or an alternating
current-to-direct current ratio of an output signal measured at a
particular wavelength.

14. The monitoring device of claim 1, wherein one or more physiological
parameters comprise one or more hemoglobin fractions.

15. The monitoring device of claim 1, wherein one or more physiological
parameters comprise one or more of oxygen saturation, blood flow, blood
volume, carboxyhemoglobin, methemoglobin, total hemoglobin, heart rate,
cardiac output, respiration, or combinations thereof.

16. The monitoring device of claim 1, herein the processing unit is
configured to dynamically configure the operational geometry of the
sensor by selectively operating one or more of the radiation sources and
one or more of the detectors to improve the optical path between the one
or more radiation sources and one or more of the detectors so as to
improve the signal-to-noise ratio of the one or more physiological
parameters of the subject.

17. The monitoring device of claim 1, wherein the processing unit is
configured to dynamically configure the operational geometry of the
sensor by selectively operating one or more of the radiation sources and
one or more of the detectors that minimize effects of large blood vessels
or static absorbers.

18. The monitoring device of claim 1, wherein the processing unit is
configured to dynamically configure the operational geometry of the
sensor by selectively operating one or more of the radiation sources and
one or more of the detectors that minimize power consumption.

19. The monitoring device of claim 1, wherein the processing unit is
configured to dynamically configure the operational geometry of the
sensor using a photon transport model.

20. The monitoring device of claim 1, wherein the processing unit
comprises a geometry controller configured to selectively operate one or
more of the radiation sources and one or more of the detectors, wherein
the geometry controller comprises one or more switching subsystems.

21. The monitoring device of claim 1, wherein the processing unit is
configured to operate the monitoring device in transmission mode by
selectively operating one or more of the radiation sources and one or
more of the detectors such that the radiation sources and the detectors
are disposed on opposite sides of a region of interest of the subject.

22. The monitoring device of claim 1, wherein the processing unit is
configured to operate the monitoring device in reflectance mode by
selectively operating one or more of the radiation sources and one or
more of the detectors such that the radiation sources and the detectors
are disposed on the same side of a region of interest of the subject.

23. The monitoring device of claim 1, wherein the processing unit is
configured to operate the monitoring device in a combined mode by
selectively operating one or more of the radiation sources and one or
more of the detectors such that the radiation sources and the detectors
are disposed on at least two sides of a region of interest of the subject
to simultaneously measure reflectance and transmission signals.

24. The monitoring device of claim 1, wherein the processing unit is
configured to generate an audio output, a visual output, an alert
message, or combinations thereof, if the quality metric associated with a
physiological parameter is outside a corresponding designated threshold.

25. The monitoring device of claim 24, wherein the processing unit is
configured to terminate the audio output, the visual output, the alert
message, or combinations thereof, if the quality metric associated with a
physiological parameter is within a corresponding designated threshold.

26. A method for monitoring a subject, comprising: selecting an initial
set of one or more radiation sources and one or more detectors for a
particular wavelength from a plurality of radiation sources and detectors
disposed on a flexible substrate in a sensor in a designated physical
arrangement; determining an initial value of one or more physiological
parameters of a subject by evaluating a region of interest of the subject
using the initial set of radiation sources and detectors; estimating a
quality metric associated with the initial value of the physiological
parameters; and dynamically configuring the operational geometry of the
sensor by controlling intensity of one or more of the radiation sources,
gain of one or more of the detectors, or a combination thereof, to
satisfy at least one quality metric associated with one or more
physiological parameters of the subject.

27. The method of claim 26, further comprising using the adaptively
configured geometry for a particular wavelength for determining
appropriate geometry for one or more other wavelengths.

28. The method of claim 26, wherein dynamically configuring the
operational geometry of the sensor comprises: iteratively selecting the
one or more further radiation sources and detectors from the plurality of
radiation sources and the one or more detectors; determining
corresponding values of one or more physiological parameters by
evaluating the region of interest of the subject using the one or more
further radiation sources and detectors for each iteration; estimating
the quality metric associated with the values of the physiological
parameters determined using the one or more further radiation sources and
detectors; and adaptively reconfiguring the operational geometry of the
sensor until the quality metric associated with the values of the
physiological parameters determined in a particular iteration is within a
designated threshold.

29. The method of claim 28, further comprising: continuously monitoring
the one or more physiological parameters of the subject using the
radiation sources and detectors used in the particular iteration
periodically estimating the quality metric associated with the values of
the physiological parameters; and adaptively configuring the operational
geometry of the sensor until the quality metric associated with the
values of the physiological parameters is within the designated
threshold.

30. A non-transitory computer readable medium that stores instructions
executable by one or more processors to perform a method for monitoring a
subject, comprising: selecting an initial set of one or more radiation
sources and one or more detectors for a particular wavelength from a
plurality of radiation sources and detectors disposed on a flexible
substrate in a sensor in a designated physical arrangement; determining
an initial value of one or more physiological parameters of a subject by
evaluating a region of interest of the subject using the initial set of
radiation sources and detectors; estimating a quality metric associated
with the initial value of the physiological parameters; and dynamically
configuring the operational geometry of the sensor by controlling
intensity of one or more of the radiation sources, gain of one or more of
the detectors, or a combination thereof, to satisfy at least one quality
metric associated with one or more physiological parameters of the
subject.

Description:

BACKGROUND

[0001] Embodiments of the present technique relate generally to
physiological monitoring, and more particularly to system and methods for
improving physiological parameter estimation using a multi-wavelength
optical transducer array.

[0002] Continual monitoring of a patient's physiological parameters such
as vital signs and/or overall health allows for accurate diagnoses and
immediate alerts for life saving interventions. Particularly, routine use
of multi-parameter monitors in trauma, surgery, and intensive-care unit
(ICU) settings has greatly improved medical outcomes in recent times.
Pulse oximeters, for example, may be used to monitor oxygen saturation
(SpO2) in arterial blood. Particularly, pulse oximeters may be used to
provide instantaneous measurements of arterial oxygenation to allow early
detection of medical conditions such as arterial hypoxemia.

[0003] Generally, the SpO2 measurements may accurately represent the
arterial oxygen saturation, even while the oxygen carrying capacity of
the blood is reduced due to low overall hemoglobin concentration.
However, in certain scenarios, use of only the SpO2 reading can be
misleading and the oxygen supply to tissues may still be inadequate
regardless of the high SpO2 value. Conventional pulse oximeters, for
example, may report erroneous SpO2 measurements due to similarities in
the absorption spectra of the oxygen carrying hemoglobin and
dysfunctional hemoglobin (dyshemoglobin) such as Carboxyhemoglobin (HbCO)
and Methemoglobin (HbMet), which are incapable of binding oxygen.

[0004] Accordingly, certain pulse oximeters have been customized to
generate multiple wavelength photoplethysmographic (PPG) pulse waveforms,
which may be related to tissue blood volume and blood flow at a
measurement site. The customized pulse oximeters use emitters sensitive
to different wavelengths for determining physiological parameters that
provide useful clinical information. However, such custom devices often
are suited only for a specific application, have poor adaptability to
different device configurations, and/or are prohibitively expensive for
routine use.

[0005] Furthermore, typical PPG-based systems are relatively large devices
including a sensor attachable to the patient and the PPG device through
one or more cables. Conventional PPG devices measure physiological
parameters such as different hemoglobin fractions by disposing the sensor
on an anatomical extremity, such as the patient's fingertip or ear. To
that end, the sensor may generally comprise two or more emitter elements,
each emitting radiation at a specific wavelength, connecting cables and a
broad spectral band photodetector common to all emitter elements for
multi-analyte measurements.

[0006] Specifically, a multiple wavelength PPG device requires
measurements at a plurality of combinations of wavelengths and different
emitter and detector placements to measure different substances in blood
without the disruptive effects of tissue motion. A large variety of
sensor types sensitive to different wavelengths, thus, may be needed to
suit different subjects and different measurement sites. Accordingly, the
choice of sensors and corresponding interface cables that may be used in
connection with one pulse oximeter device may be rather extensive, thus
impeding the portability and cost-effectiveness of the device.
Additionally, the complicated reconfiguration of the pulse oximeter
device for appropriately selecting and positioning the sensors and cables
at the patient extremity for making a plurality of measurements may
significantly add to patient discomfort.

[0007] Due to cost and complicated configuration concerns, conventional
pulse oximeters are typically known to be used only in hospital
environments by experienced medical professionals. Use of the pulse
oximeters outside of high acuity hospital wards, however, has been
limited owing to unsuitable power consumption, cost, form factor, and
performance of the devices. In particular, power and performance of such
physiological monitors may be limited by conventional device
configurations, while corresponding measurements may often be distorted
by tissue motion artifacts.

[0009] Certain aspects of the present technique are drawn to a monitoring
device including at least one sensor configured to monitor one or more
physiological parameters of a subject and a processing unit operatively
coupled to the sensor. The sensor comprises a plurality of radiation
sources and detectors disposed on a flexible substrate in a designated
physical arrangement. The processing unit is configured to dynamically
configure an operational geometry of the sensor by controlling the
intensity of one or more of the radiation sources and the gain of one or
more of the detectors so as to satisfy at least one quality metric
associated with one or more physiological parameters of the subject.

[0010] Certain other aspects of the present technique are directed to a
method for monitoring a subject. An initial set of one or more radiation
sources and one or more detectors for a particular wavelength are
selected from a plurality of radiation sources and detectors disposed on
a flexible substrate in a sensor in a designated physical arrangement. An
initial value of one or more physiological parameters of a subject is
determined by evaluating a region of interest of the subject using the
initial set of radiation sources and detectors. Additionally, a quality
metric associated with the initial value of the physiological parameters
is estimated. Further, the operational geometry of the sensor is
dynamically configured by controlling intensity of one or more of the
radiation sources, gain of one or more of the detectors, or a combination
thereof, to satisfy at least one quality metric associated with one or
more physiological parameters of the subject.

[0011] Certain further aspects of the present technique are drawn to a
non-transitory computer readable medium that stores instructions
executable by one or more processors to perform a method for monitoring a
subject.

DRAWINGS

[0012] These and other features, aspects, and advantages of the present
technique will become better understood when the following detailed
description is read with reference to the accompanying drawings in which
like characters represent like parts throughout the drawings, wherein:

[0013]FIG. 1 is a schematic diagram of an exemplary system for monitoring
one or more physiological parameters of a subject, in accordance with
aspects of the present system;

[0014]FIG. 2 is a schematic diagram illustrating an exemplary position of
the sensor of FIG. 1 at a measurement site of the subject, in accordance
with aspects of the present system;

[0015]FIG. 3 is a schematic diagram of an exemplary sensor used in the
system of FIG. 1 in accordance with aspects of the present system;

[0016]FIG. 4 is a flow chart illustrating an exemplary method for
monitoring one or more physiological parameters of the subject, ire
accordance with aspects of the present technique;

[0017]FIG. 5 illustrates exemplary configurations of an operational
geometry of the sensor that may be dynamically configured to satisfy a
desired quality metric, in accordance with aspects of the present
technique; and

[0018]FIG. 6 illustrates a graphical representation depicting an
exemplary PPG waveform plotted using amplitudes of received PPG signals
over time in one exemplary implementation, in accordance with aspects of
the present technique.

DETAILED DESCRIPTION

[0019] The following description presents system and methods for
non-intrusive monitoring one or more physiological parameters of a
subject, for example a person. To that end, the physiological parameters,
for example, include SpO2, one or more hemoglobin fractions, total
hemoglobin concentration, HbCO concentration, methemoglobin
concentration, and/or other parameters related to blood flow, blood
volume and blood or tissue constituents. Particularly, certain
embodiments illustrated herein describe inexpensive yet efficient methods
and systems that allow continuous monitoring of the physiological
parameters of the subject using a multi-wavelength optical transducer
array.

[0020] For discussion purposes, embodiments of the present system are
described with reference to a photoplethysmograph (PPG). However, in
certain other embodiments, the present system may include any other
suitable monitoring device, such as a pulse oximeter and/or a hemoglobin
monitor for monitoring the subject in different operating environments.
An exemplary environment that is suitable for practicing various
implementations of the present system and methods is described in the
following sections with reference to FIG. 1.

[0021]FIG. 1 illustrates an exemplary monitoring system 100 for
non-intrusive monitoring of one or more physiological parameters of a
subject 102 (patient) such as a person. In the present description,
variations of the terms "non-intrusive," and "non-invasive" monitoring
are used interchangeably to refer to measuring the one or more
physiological parameters with negligible direct physical contact with the
patient 102. Accordingly, in one embodiment, the system 100, for example,
includes a wearable pulse oximeter device for continuous monitoring of
SpO2 in the subject's blood. In another embodiment, the system 100
includes a PPG sensor 104 configured to measure, for example, the total
hemoglobin concentration and/or different hemoglobin fractions in the
patient's blood.

[0022] To that end, the sensor 104 includes a substrate 106, and a
plurality of radiation sources 108 and one or more detectors 110 disposed
on the substrate 106 for monitoring the one or more physiological
parameters of the patient 102. In certain embodiments, the sensor 104 is
a flexible device that is generally positioned at one or more extremities
of the patient. Typically, the extremities correspond to tissue regions
with a rich presence of capillaries and arterioles. Such regions, for
example, include distal regions of the digits, forehead, earlobe, and
nose that tend to demonstrate the strongest pulse amplitudes especially
in the absence of vasoconstriction, which may affect most of these
locations.

[0023]FIG. 2, for example, illustrates an embodiment of the sensor 104 of
FIG. 1. Particularly, FIG. 2 illustrates the sensor 104 as a lightweight
and flexible device positioned around the fingertip 202 of the patient
102 where strong pulsatile signals may be observed for accurate
measurements. The flexibility of the sensor 104 allows comfortable
placement of the device over the patient's measurement site. Furthermore,
in addition to the illustrated position of the sensor 104 configured for
use on opposing surfaces on the patient's fingertip, in certain
embodiments, the sensor 104 may be configured for use on adjacent
surfaces at the patient's measurement site relative to the excitation.

[0024] Further, FIG. 3 illustrates one or more exemplary components of the
flexible sensor 104 for use in continuous and non-invasive monitoring of
the physiological parameters of the patient 102. To that end, as
previously noted, the sensor 104 includes the substrate 106, for example,
including a flexible polyimide material. The sensor 104 also includes the
plurality of radiation sources 108, and one or more detectors 110
disposed on the flexible substrate 106 in a designated physical
arrangement. Additionally, the sensor 104 includes an interconnect 302,
for example, an electrical interconnect designed to allow the radiation
sources 108 and the detectors 110 to be addressed individually or by
using common connections for serial or parallel configurations.

[0025] Although, FIG. 3 illustrates the sensor 104 having the flexible
substrate 106, in certain embodiments, the sensor 104 may include one or
more regions having a rigid substrate in addition to the flexible
substrate 106. In one embodiment, for example, the substrate 106 may
include one or more rigid portions in regions where the sources 108
and/or detectors 110 are disposed, while including one or more flexible
portions in between the sources 108 and/or the detectors 110 for the
interconnect 302.

[0026] The radiation sources 108, for example, include optical devices
such as light emitting diodes (LEDs), organic-LEDs (OLEDs) and/or laser
diodes of different wavelengths. In one embodiment, the wavelengths of
the radiation sources 108 are in the visible and infrared (IR) spectrum.
In another embodiment, the wavelengths of the radiation sources 108 are
selected as per application requirements. Additionally, in certain
embodiments, each of the radiation sources 108 generates radiation at one
or more single wavelengths. In certain other embodiments, the radiation
sources 108 are configured to generate broadband light. Certain exemplary
radiation sources for use in one embodiment of the sensor 104 to allow
for the multiple wavelength measurements are listed in the following
table 1.

[0027] Further, the detectors 110 may include photodetectors 110 such as a
silicon photodiode, an organic photodiode, or any other suitable
detection device sensitive to single wavelengths or broadband light.
Particularly, in one embodiment, a single, wide area detector may be
employed to maximize light collection, thus improving performance. In
another embodiment, multiple smaller area detectors may be operated
simultaneously and the measured signals may be combined by analog or
digital means to approximate a larger area detector.

[0028] It may be noted that the underlying science of pulse oximetry is
based on a manipulation of the Lambert-Beer law, which describes the
attenuation of light traveling through a mixture of absorbers.
Accordingly, signals from detected light that travels through
blood-perfused tissues of interest of the patient 102 can be used to
estimate, for example, the underlying arterial hemoglobin composition.
However, light scatters when travelling through the tissues and
influences some of the simplifications made in determining the
relationship between the detected attenuation and the underlying arterial
hemoglobin composition.

[0029] Under most clinical circumstances, an empirical process used by the
manufacturers during design to calibrate a conventional pulse oximetry
system substantially accommodates the scattering in resulting readings.
The quality of the plethysmographic signal, however, may still be
affected by the presence of certain factors, for example, the spacing
between the radiation sources 108 and the detectors 110 on the flexible
substrate 106, the magnitude of the periodic increase and decrease in the
tissue blood fraction, the extinction coefficient of the modulating blood
volume at a particular measurement wavelength, local vessel compliance
and/or venous pulsation.

[0030] Further, large pulsating vessels may also affect the quality of the
plethysmographic signal. Although large pulsating vessels contribute to
the optical pulse, these vessels often disrupt pulse oximetry
measurements and are typically absent from common capillary measurement
sites such as the distal regions of the finger or toe where strong
pulsatile signals are commonly observed. Thus, the relative placement of
the radiation sources 108 and the detectors 110 with respect to each
other and the location of the radiation sources 108 and the detectors 110
relative to large blood vessels determines the ability of the system 100
to obtain high-quality plethysmographic signals.

[0031] Determining a suitable sensor position in conventional pulse
oximetry devices, however, may require positioning and subsequent
repositioning of multiple components such as emitters, detectors,
housings and connecting cables at one or more measurement sites, thus
distressing the patient 102. Unlike such large conventional pulse
oximetry devices, embodiments of the present system 100 include low-cost
disposable physiological monitors such as the flexible sensor 104 that
can be attached to a desired measurement site with negligible discomfort
to the patient 102. Particularly, the flexible sensor 104 allows for
accurate physiological parameter measurements at multiple wavelengths
without the need for further repositioning of the sensor 104 at different
measurement positions.

[0032] Accordingly, in one embodiment, the sensor 104 is fabricated by
disposing the radiation sources 108 and the detectors 110, sensitive to
multiple wavelengths, on the flexible substrate 106 using a roll-to-roll
fabrication technique. To that end, semiconducting wafer-based processing
is modified for a hybrid assembly approach compatible with low-cost
capabilities of roll-to-roll manufacturing to provide high performance
physiological sensors at affordable costs. The hybrid approach enables
use of the best-suited electronic technologies for different functions.
By way of example, in the hybrid approach, silicon-bipolar for analog
circuits, silicon complementary metal oxide semiconductor (CMOS) for
digital circuits, Gallium Arsenide (GaAs) for high frequency operations,
and/or Aluminum Gallium Arsenide (AlGaAs) for optical components may be
combined in a heterogeneous manner to provide a high performance and
cost-effective physiological sensor.

[0033] In another embodiment, the radiation sources 108 and detectors 110
are disposed on the flexible substrate 106 using a magnetically directed
self-assembly (MDSA) technique by embedding micromagnets into the
flexible substrate 106 and correspondingly embedding micromagnets into
the sources 108 and detectors 110. Use of the MSDA technique allows for
fabrication of the lightweight and flexible sensor 104 including a
plurality of co-located radiation sources 108 and detectors 110 sensitive
to one or more wavelengths. MSDA provides strong attraction, desired
orientation and reliable attachment of the radiation sources 108 and the
detectors 110 to the flexible substrate 106. An additional advantage of
MDSA is the relative insensitivity of magnetostatic binding forces
towards external perturbations such as surface contamination, trapped
charge, conductivity, and pH, presence of other non-magnetic materials or
nearby binding sites.

[0034] In a further embodiment, the radiation sources 108 and detectors
110 are disposed on the flexible substrate 106 in a designated physical
arrangement using electrical and/or mechanical means. Although only few
exemplary fabrication techniques are described herein, in certain other
embodiments, the sensor 104 may be fabricated using any other
conventional manufacturing technique that allows for fabrication of the
lightweight and flexible sensor 104 including a plurality of co-located
radiation sources 108 and detectors 110 sensitive to one or more
wavelengths.

[0035] Further, in certain embodiments, the sensor 104 is fabricated such
that the radiation sources 108 and detectors 110 are disposed on the
flexible substrate 106 in a designated physical arrangement to allow
multiple measurements without physically moving the sensor 104 to a
different measurement position, in one embodiment, for example, the
radiation sources 108 and detectors 110 are arranged as a pixelated
optical transducer array of large area (for example, of about 1
centimeter squared (cm2)) on the flexible substrate 106 to reduce
tissue motion artifacts and improve light collection efficiency. In
another embodiment, the radiation sources 108 and detectors 110 sensitive
to different wavelengths, for example, are embedded individually or in
specific groups in an array in the flexible substrate 106. In certain
other embodiments, the radiation sources 108 and the detectors 110
sensitive to different wavelengths are placed within the array in an
interleaving manner. In further embodiments, the distances between the
radiation sources 108 and the detectors 110 are configured to be of
various lengths to allow different depths of light penetration into the
target tissue.

[0036]FIG. 3, for example, illustrates an exemplary physical arrangement
of the radiation sources 108 and the detectors 110 on the flexible
substrate 106. Particularly, FIG. 3 depicts the radiation sources 108 and
detectors 110 arranged in two 10×10 arrays 304 on the flexible
substrate 106. Although FIG. 3 illustrates two 10×10 arrays 304, in
certain embodiments, a fewer or greater number of the radiation sources
108 and detectors 110 may be incorporated onto an appropriately sized
flexible substrate to extend the sensor functionality to different
monitoring applications.

[0037] In certain embodiments, for example, the radiation sources 108 and
detectors 110 arranged on the flexible substrate 106 to operate in a
reflectance and/or a transmission mode. Particularly, in one embodiment,
the sensor 104 operates in transmission mode (see FIG. 2) where the
radiation sources 108 and detectors 110 are operated on opposite sides of
the tissue, for example, for measuring light transmission through a
finger or an earlobe. Alternatively, the sensor operates in reflectance
mode where the radiation sources 108 and detectors 110 are operated on
the same side of the tissue, for example,for measuring light reflection
from the forehead or the sternum. In a further embodiment, the sensor 104
operates in a combined mode where the radiation sources 108 and detectors
110 are operated on both sides of the tissue to simultaneously measure
reflectance and transmission signals.

[0038] Use of the collocated radiation sources 108 and detectors 110
operating at multiple wavelengths, thus, allows for measurement of
different optical absorption and scattering characteristics of the target
issue and corresponding constituents such as cells, blood, and
interstitial fluid. Additionally, presence of a plurality of the
radiation sources 108 and the detectors 110 capable of operating at
multiple wavelengths allows for redundancy, thus improving the
reliability of the system 100. Particularly, in case of failure of one or
more components, the system 100 may selectively operate the remaining
radiation sources 108 and the detectors 110 so as to provide the desired
gain and intensity characteristics for measuring physiological parameters
of interest.

[0039] Further, in certain embodiments, optically opaque barrier materials
(not shown) may be used to prevent direct coupling of adjacent radiation
sources 108 and detectors 110 using an under-fill or intra-fill technique
to further ensure the accuracy of the measurements. Additionally, use of
the large area, arrayed radiation sources 108 and detectors 110 reduces
distortions caused by the tissue motion typically observed in single
source, single detector point-to-point measurements. The resulting
multiple wavelength measurements, thus, can be used to improve pulse
oximetry measurements and in many other multi-parameter spectroscopic
applications.

[0040] Particularly, certain spectroscopic applications may often require
multiple wavelength measurements for estimating different hemoglobin
fractions or to maximize sensitivity by improving the quality metrics
such as signal-to-noise ratio (SNR) of a resulting waveform. Conventional
pulse oximetry devices, however, may require extensive rearrangement of
corresponding sources 108 and the detectors 110 for multiple wavelength
measurements. In particular, the sources 108 and the detectors 110 may
need to be physically moved to a different measurement site, for example,
for mitigating the disruptive effects caused due to the presence of a
large pulsating blood vessel. Such repeated rearrangements, however, may
cause discomfort to the patient 102 and may require the presence of a
trained medial professional.

[0041] In contrast to such conventional pulse oximetry devices that
require extensive rearrangement, the system 100 of FIG. 1 allows for
dynamic reconfiguration of the operational geometry of the radiation
sources 108 and the one or more detectors 110 in the sensor 104 without
physically moving the sensor 104 to different measurement positions. As
used herein, the term "operational geometry" refers to a subset of the
radiation sources 108 and detectors 110, selected from the plurality of
radiation sources 108 and detectors 110 disposed on the flexible
substrate 106, which when operational, provide desired location and
intensity characteristics.

[0042] Accordingly, in an embodiment such as illustrated in FIG. 1, the
system 100 includes a geometry controller 112 coupled to a processing
unit 114 that adaptively reconfigures the operational geometry of the
radiation sources 108 and the detectors 110 to satisfy one or more
quality metrics of the physiological parameters of interest. Accordingly,
in certain embodiments, the processing unit 114 estimates the quality
metrics, such as, SNR, amplitude or an alternating current-to-direct
current (AC-to-DC) ratio of an output signal measured at a particular
wavelength. The estimated quality metrics are then compared against
corresponding thresholds or desired values. If the quality metrics are
outside the corresponding thresholds, the processing unit 114 uses the
geometry controller 112 to reconfigure the operational geometry of the
sensor 104 (sensor geometry) to optimize the quality metrics.

[0043] To that end, in one embodiment, the geometry controller 112
includes, for example, a switching subsystem 118 including a plurality of
switches and one or more radiation source drivers 120 coupled to the
sensor 104 through one or more interfaces such as the interconnect 302
illustrated in FIG. 3. The drivers 120, in one embodiment, include a
self-contained power supply having outputs matched to the electrical
characteristics of the corresponding radiation sources 108. In certain
embodiments, the drivers 120 may include more than one channel for
separate control and/or adjustment of not only the activation and
deactivation, but also the gain and/or intensity of the different
radiation sources 108 and detectors 110.

[0044] In one embodiment, for example, the system 100 employs the drivers
120 along with the plurality of switches to selectively operate the
radiation sources 108 and the detectors 110 either individually, in
specific groups, and/or by using common connections for serial or
parallel configurations. In another embodiment, the processing unit 114
adaptively reconfigures the sensor geometry to optimize the excitation
patterns by selectively operating only those radiation sources 108 and
the detectors 110 that contribute significantly to the plethysmographic
signal. Particularly, in certain embodiments, the processing unit 114
selects the radiation sources 108 and the detectors 110 that optimize the
optical paths through the target tissue to minimize the effects of large
blood vessels and other large static absorbers.

[0045] In one embodiment, the processing unit 114 performs the optical
path optimization using pre-determined information stored in a memory
device 116. In certain embodiments, the memory device 116 may include
storage devices such as RAM, ROM, disc drive, solid-state drive and/or
flash memory. Further, the processing unit 114 includes, for example, one
or more microprocessors, microcomputers, microcontrollers, field
programmable gate arrays, application specific integrated arrays, or any
other suitable device for performing the optimization. Particularly, the
processing unit 114 optimizes the optical paths so as to improve the
quality metric of the physiological parameters of interest and/or the
power efficiency of directing and collecting transmitted or reflected
light.

[0046] To that end, in certain embodiments, the processing unit 114
employs one or more photon transport models to investigate the effects of
the placement of the radiation sources 108 and the detectors 110 on the
quality of the output signals. Photon transport models, for example, may
include Monte Carlo simulations, finite-difference time domain models, as
well as analytical solutions and diffusion approximations of radiative
transfer equations.

[0047] Particularly, in one embodiment, the processing unit 114 uses the
Monte Carlo methods to simulate photon transport for multiple
wavelengths. The processing unit 114, for example, uses optical path
length data corresponding to each wavelength to account for the
non-linearity of photon transport through the tissue while performing
multi-analyte measurements. The processing unit 114 then optimizes the
source-detector configuration based on the specific geometry
(transmission or reflection) of the sensor 104 using Monte Carlo
simulations. Subsequently, based on the quality metrics estimated for the
initial measurements, the processing unit 114 reconfigures the sensor
geometry to operate the radiation sources 108 and/or the detectors 110 as
large area, or distributed devices that maximize optical generation and
light capture efficiency, while reducing tissue motion artifacts.

[0048] In certain embodiments, the processing unit 114 employs the
reconfigured sensor geometry corresponding to one wavelength for
determining the geometry configurations for the other wavelengths. Here,
it may be noted that spectroscopic applications entailing measurement of
different optical absorption and scattering characteristics of a target
tissue and its constituents often require measurements at multiple
wavelengths. To that end, in one embodiment, the processing unit 114
iteratively operates one or more combinations of the radiation sources
108 and the detectors 110 of different wavelengths through substantially
the same path through the target tissue. In every iteration, the incident
radiation undergoes attenuation, which may be dependent, among other
things, on the wavelength of the light, the type and concentration of the
substances within the target tissue, and the volume changes in the
arterial bloodstream.

[0049] The impinging radiation is then received and processed by the
detectors 110 for further use. In one embodiment, for example, the
received signal is band-pass filtered using one or more filters 122 to
segregate the signal information from noise, interference and/or motion
artifacts. The filtered signals are then appropriately amplified and
converted into digital signals, for example, using an analog-to-digital
converter (ADC) 124 for further evaluation. In certain embodiments, the
processing unit 114 analyzes the digitized signals using one or more
stored procedures to determine if the quality of the physiological
parameter measurements is within one or more desired or a designated
threshold values.

[0050] As previously noted, based on the estimated quality metrics, the
processing unit 114 may adaptively reconfigure the geometry of the
radiation sources 108 and the detectors 110 to optimize the physiological
parameter measurements for a particular wavelength over one or more
iterations. The processing unit 114 then uses the reconfigured geometry
to determine suitable sensor geometry for other wavelengths so as to
estimate values of the physiological parameters, such as the oxygen
saturation, heart rate, blood pressure, cardiac output, respiration
and/or hemoglobin concentration.

[0051] In one embodiment, the processing unit 114 the displays the
estimated values on an input-output (I/O) interface 126 coupled to the
system 100. In another embodiment, the processing unit 114 stores the
determined information for later review and analysis in the memory device
116. In certain other embodiments, the processing unit 114 communicates
the determined information to another location such as local or remotely
located hospital information system over a communications link (not
shown). To that end, the communication link, for example, may include
wired networks such as LAN and cable, wireless networks such as WLAN,
cellular networks, satellite networks, and/or short-range networks such
as ZigBee wireless sensor networks.

[0052] Additionally, in certain embodiments, the processing unit 114 may
also generate an alert through the I/O interface 126 if values of any of
the physiological parameters are determined to be outside designated
thresholds. Particularly, in one embodiment, the processing unit 114
generates an audio and/or a visual alert such as flashing lights, sounds
an alarm, and/or sends a voicemail, text messages and/or email to a
mobile device of appropriate personnel and/or to another health
information system through a wired and/or wireless communications link.

[0053] Embodiments of the system 100 allow for selective excitation of the
sensor components to ensure that only the necessary subset of all
available radiation sources 108 are used at any time, thus minimizing the
power consumption of the entire PPG module. Similarly, on the detection
side, the selective use of the detectors 110 allows for a desired
detection efficiency by effectively increasing the detection area, while
at the same time keeping the detectors 110 that do not significantly
contribute to the overall signal off to reduce power consumption.

[0054] Furthermore, the reconfigurable geometry of the sensor 104 also
minimizes the effects of large static absorbers, which negatively affect
the quality of the signals and consequently the accuracy of the estimated
physiological parameters. The overall adaptive nature of the
excitation/detection patterns, thus, enables the collection of high
quality signals with the minimal power consumption to allow fabrication
of low-power battery-operable monitoring devices that provide greater
signal fidelity, ease of usage and patient comfort.

[0055] Although FIG. 1 illustrates an embodiment of the system 100 as a
stand-alone device, in certain embodiments, the system 100 can be
operationally coupled with other devices and systems that can be
non-invasive and/or invasive and provide additional data that can be
processed by the processing unit 114 or by some central processing
section to enable more comprehensive monitoring, assessment, diagnosis,
and/or preventative care. The functioning of an exemplary system for
monitoring the physiological parameters of a subject and assessing a
health condition of the patient 102, in accordance with aspects of the
present technique, is described in greater detail with reference to FIG.
4.

[0056]FIG. 4 illustrates a flow chart 400 depicting an exemplary method
for monitoring the physiological parameters of a subject using a
dynamically configurable, multi-source, multi-detector arrayed PPG
sensor. To that end, embodiments of the exemplary method may be described
in a general context of computer executable instructions on a computing
system or a processor. Generally, computer executable instructions may
include routines, programs, objects, components, data structures,
procedures, modules, functions, and the like that perform particular
functions or implement particular abstract data types.

[0057] Certain embodiments of the exemplary method may also be practiced
in a distributed computing environment where optimization functions are
performed by remote processing devices that are linked through
communications network. In the distributed computing environment, the
computer executable instructions may be located in both local and remote
computer storage media, including memory storage devices. The computer
executable instructions, for example, may be stored or adapted for
storage on one or more tangible, machine readable media such as data
repository chips, local or remote hard disks, optical disks (compact
disks or digital versatile disks), solid state devices, or other suitable
media, which may be accessed by a processor-based system to execute the
stored instructions.

[0058] Further, in FIG. 4, the exemplary method is illustrated as a
collection of items in a logical flow chart, which represents operations
that may be implemented in hardware, software, or a combination thereof.
In the context of software, the blocks represent computer instructions
that, when executed by one or more processing systems, perform the
recited operations. The order in which the exemplary method is described
is not intended to be construed as a limitation, and any number of the
described items may be combined in any order to implement the exemplary
method disclosed herein, or an equivalent alternative method.
Additionally, certain items may be deleted from the exemplary method
without departing from the spirit and scope of the subject matter
described herein. For discussion purposes, the exemplary method is
described with reference to the implementations of FIGS. 1-3.

[0059] In one embodiment, a healthcare monitoring system, such as the
system 100 of FIG. 1, continually monitors one or more physiological
parameters of a subject. To that end, the monitoring system 100 employs,
for example, a dynamically configurable, multi-source, multi-detector
arrayed PPG sensor 104 such as the sensor 104 of FIG. 1. As described
with reference to FIGS. 1-3, the PPG sensor 104 includes a plurality of
co-located and independently operable radiation sources 108 and detectors
110 of different wavelengths disposed on the flexible substrate 106 in a
designated physical arrangement for physiological monitoring.

[0060] Traditional PPG devices measure oxygen saturation (SpO2) in
arterial blood non-invasively and continuously by a sensor attached to
the finger or ear. Clinically, SpO2 has been used as an indication of the
oxygen supply to tissues. Particularly, high oxygen saturation and strong
and regular peripheral pulsation are clinical signs that have been used
to reflect adequate oxygenation of blood in the lungs and sufficient
cardiac function to supply oxygen rich blood to tissues. However, use of
only the SpO2 reading can be misleading and the oxygen supply to tissues
may still be inadequate regardless of the high SpO2 value.

[0061] Particularly, conventional pulse oximeters may report high SpO2
values even though the oxygen carrying capacity is low. These erroneous
SpO2 measurements may occur due to the similarities in the absorption
spectra of the oxygen carrying hemoglobin and the dysfunctional
hemoglobin (dyshemoglobin), such as HbCO and HbMet, which are incapable
of binding oxygen. In certain scenarios, a high SpO2 reading even in the
absence of dyshemoglobin does not guarantee sufficient oxygenation of
tissues if the total hemoglobin concentration is low. Conventional
noninvasive pulse oximeters, thus, may not be able to quantify the amount
of oxygen delivered and utilized by the tissue consistently, and
therefore, may require additional tissue and/or blood samples to confirm
the adequacy of tissue oxygenation.

[0062] Unlike such conventional monitoring devices, the dynamically
configurable, multi-source, multi-detector arrayed PPG sensor 104
described herein finds uses beyond traditional pulse-oximetry
applications for assessing a variety of health conditions using multiple
wavelength measurements. In one embodiment, for example, the PPG sensor
104 may be used as a potential diagnostic tool to detect clinically
significant hypovolemia before the onset of cardiovascular
decompensation.

[0063] To that end, at step 402, the processing unit 114 selects an
initial set of one or more radiation sources and detectors sensitive to a
particular wavelength from the plurality of radiation sources 108 and
detectors 110 embedded in the flexible substrate 106 in a designated
physical arrangement, for example, as depicted by the array 304 of FIG.
3. The overall absorption is typically higher at lower wavelengths.
Accordingly, in one embodiment, the processing unit 114 selects the
initial set of one or more radiation sources 108 and detectors 110 that
are sensitive to a lower wavelength, for example, at about 630 nm. In
certain embodiments, the processing unit 114 uses a designated wavelength
typically used to measure a specific physiological parameter being
monitored as the initial wavelength. In certain other embodiments, the
processing unit 114 may use a user-supplied wavelength as the initial
wavelength.

[0064] Further, at step 404, the processing unit 114 configures the
monitoring system 100 to use the initial set of radiation sources 108 to
irradiate the target tissue. An initial set of detectors 110 receive and
process the impinging radiation for further evaluation. In one
embodiment, for example, the received signal is filtered, amplified and
converted into digital signals for determining an initial value of the
one or more physiological parameters of the subject. The physiological
parameters, for example, may include oxygen saturation, heart rate,
cardiac output, respiration, and/or other parameters related to blood
flow, blood volume and blood or tissue constituents.

[0065] Further, at step 406, the processing unit 114 estimates a quality
metric associated with the initial values of the physiological
parameters. Particularly, the processing unit 114 may estimate the
quality metrics continuously or periodically for assessing the quality of
the measured physiological parameter values. In one embodiment, for
example, the processing unit 114 monitors the SNR of the determined
physiological parameter values continuously. In another embodiment, the
processing unit 114 determines the optical power received at the
receiving end, or the amplitude of the received signal to determine
corresponding quality metrics. In certain other embodiments, the
processing unit 114 uses the AC component, or the ratio of the AC
component to the DC component of the signal (or the normalized signal)
for one or more wavelengths to determine the quality metric associated
with the physiological parameter of interest such as a relative
concentration of the hemoglobin species in the blood.

[0066] Additionally, the processing unit 114 may compare the determined
quality metrics with the corresponding threshold or desired values
defined as per application and/or user specified requirements. In certain
embodiments, the processing unit 114 may determine if two or more quality
metrics such as the optical power and the corresponding AC-to-DC
component of the output signal are within the designated thresholds. If
the quality metrics determined from the initial configuration are outside
designated thresholds, at step 408, the processing unit 114 dynamically
reconfigures the geometry by selectively operating one or more further
radiation sources 108 and/or one or more detectors 110 selected from the
plurality of radiation sources 108 and detectors 110.

[0067] Particularly, the processing unit 114 reconfigures the sensor
geometry to satisfy the quality metric associated with values of the
physiological parameters measured using the further radiation sources 108
and detectors 110. In one embodiment, for example, the processing unit
114 reconfigures the sensor geometry such that the SNR of the
physiological parameters measured using the further radiation sources 108
and detectors 110 is within a desired range. In another embodiment, the
processing unit 114 may reconfigure the geometry such that the output
signals have a desired AC-to-DC component while the power consumption of
the monitoring system 100 is minimized.

[0068] One or more suitable techniques may be employed to optimize the
sensor geometry. In one embodiment, for example, the processing unit 114
employs Monte Carlo simulations to determine the most appropriate
combination of the radiation sources 108 and the detectors 110 that allow
for optimization of the desired quality metrics. The processing unit 114
performs Monte Carlo simulations, for example, to investigate the effects
of the placement of the arrayed radiation sources 108 and detectors 110
on the quality of the signals. The simulations then allow the processing
unit 114 to optimize the source-detector separation based on the specific
geometry (transmission or reflection) of the PPG sensor 104. By way of
example, in an exemplary implementation, Monte Carlo simulations were
performed to obtain the predicted plethysmographic signals for the
wavelengths 613 nm, 632 nm, 660 nm, 690 nm, 730 nm, 760 nm, 800 nm and
900 nm.

[0069] Accordingly, in one embodiment, the processing unit 114 selects the
sensor wavelengths for adaptive reconfiguration from among the available
radiation sources 108 of high emissivity. Particularly, the wavelengths
are selected so as to provide good coverage over the range in which the
tissue transmission is high enough, for example, from about 600 to about
1000 nm in a specific application. Additionally, in certain embodiments,
the center wavelengths are optimized to locate at, or proximal the
isobestic wavelengths of the physiological parameter of interest, for
example, hemoglobin derivatives. The wavelengths are further optimized to
avoid regions where the changes in the total blood and tissue absorptions
are prominent, thus minimizing the effects of possible wavelength shifts
in the radiation sources 108.

[0070] Furthermore, in certain embodiments, the processing unit 114
reconfigures the sensor geometry to operate the radiation sources 108
and/or the detectors 110 as large area or distributed devices so as to
maximize the efficiency of directing and collecting transmitted or
reflected light. In an alternative embodiment, a single large area
detector may be used to maximize light collection. By way of example,
FIGS. 5 and 6 illustrate exemplary reconfigurations of the sensor
geometry using the method of FIG. 4 for measuring physiological
parameters such as HbCO concentration in the patient's blood.

[0071] Particularly, FIG. 5 illustrates certain exemplary configurations
500 of the operational geometry of the sensor 104 that may be dynamically
configured to satisfy a desired quality metric for measuring arterial
blood components of interest. In the embodiment illustrated in FIG. 5,
the sensor 104 includes six radiation sources 108 and one or more
detectors (not shown) capable of receiving different wavelengths emitted
by the radiation sources 108.

[0072] In one embodiment, for example, three of the radiation sources 108
are configured to emit a first wavelength λ1, whereas the
other three radiation sources 108 are configured to emit a second
wavelength λ2. Further, the radiation sources 108 are arranged
on the flexible substrate 106, for example, in a symmetrical arrangement
such that an optimal operating configuration at one wavelength may be
used as a baseline operating configuration for determining optimal
configurations for other wavelengths. To that end, in one embodiment, the
processing unit 114 iteratively reconfigures operational geometry of the
sensor 104 into different configurations 502-516 by selectively operating
the radiation sources 108 and detectors to maximize the quality metric.

[0073]FIG. 6 illustrates a graphical representation 600 depicting an
exemplary PPG waveform 602 plotted using the amplitude of received PPG
signals over time in an exemplary implementation. Particularly, the PPG
waveform 602, as illustrated in FIG. 6, includes a DC component 604
attributed to the reflectance, absorbance or transmittance of light from
static tissues and fluids within the optical path. The PPG waveform 602
also includes an AC component 606 attributed to the reflectance,
absorbance or transmittance of light from pulsating arterial blood. In
the exemplary implementation, quality metric is chosen to maximize the
AC-to-DC ratio in order to increase sensitivity to arterial blood
components.

[0074] To that end, as illustrated in the configuration 502 of FIG. 5, for
example, a first radiation source 518 of the first wavelength
λ1 is operated and the resulting quality metric is observed
over an epoch duration 608 of several arterial pulses. The processing
unit 114 then reconfigures sensor geometry into a configuration 504 so as
to adjust the intensity of the first radiation source 518 to determine
one or more operational settings at which the quality metric is
maximized. Further, the processing unit 114 reconfigures the sensor
geometry into a configuration 506, in which a second radiation source 520
of the first wavelength λ1 is operated simultaneously with the
first radiation source 518 and the corresponding quality metric is
observed.

[0075] In another configuration 508, the intensity of the second radiation
source 520 is adjusted to determine the operational settings at which the
quality metric is maximized. Further, in a subsequent configuration 510,
the sensor geometry is reconfigured by operating a third optical source
522 of the first wavelength λ1 simultaneously with the first
and second radiation sources 518, 520 and determining the corresponding
quality metric. Similarly, at a configuration 512, the intensity of the
third radiation source 522 is adjusted to determine the operational
settings of the sensor 104 at which the AC-to-DC ratio is maximized.

[0076] A final operating configuration 514 then becomes the baseline
configuration for the first wavelength, λ1. Further, in
certain implementations, the corresponding symmetric operational
configuration may be used as a baseline configuration for the second
wavelength, λ2. The processing unit 114 estimates the quality
metric over time, while adjusting the intensities of the radiation
sources 518, 520 and 522, either independently or simultaneously, so as
to maximize the quality metric during the course of operation. Although
the embodiment described with reference to FIG. 5 describes the quality
metric for the first and second wavelengths λ1 and
λ2 to be in a symmetric configuration, in certain
implementations, the quality metrics may differ from a baseline depending
on the continual measurements.

[0077] Adaptive reconfiguration of the geometry, thus, allows optimization
of the excitation patterns by selectively operating only those radiation
sources 108 and the detectors 110 that contribute significantly to the
plethysmographic signal. It may be noted that much of the power
inefficiency in a conventional PPG device is due to excitation of all the
radiation sources and signal processing of the measured signals.
Accordingly, selective operation of a subset of the sensor components, in
one embodiment, minimizes the power consumption to allow use of a
ubiquitous, wearable and battery-powered monitoring device.

[0078] Further, in certain embodiments, the processing unit 114 adaptively
reconfigures the sensor geometry continually, periodically, or when the
desired quality metrics fall or remain outside their designated
thresholds for more than a designated period of time, thus further
improving the power consumption. Additionally, selective operation of a
subset of the sensor components optimizes the optical path, in turn
minimizing the effects of large blood vessels and other large static
absorbers on the output physiological parameter values measured using a
particular wavelength. The optical path optimization reduces motion
artifacts to allow for high-fidelity signal measurements.

[0079] Many spectroscopic applications, however, require measurements from
multiple wavelengths to estimate a variety of hemoglobin fractions for
assessing different and complicated health conditions of the patient. The
fundamental principle of photoplethysmography is that light of different
wavelengths traverses the same path through the target tissue so as to
interrogate the same volume for obtaining accurate physiological
parameter measurements. The collocation of the radiation sources 108 and
detectors 110 on the flexible substrate allows for similar path lengths
through the target tissue. Accordingly, in certain embodiments, the
processing unit 114 employs the reconfigured geometry configurations from
one wavelength to determine the geometry configuration for other
wavelengths of interest for multi-analyte measurements.

[0080] Particularly, in one embodiment, the processing unit 114 analyzes
the alterations in the PPG waveform measured at different wavelengths to
track progressive reductions in central blood volume. In another
embodiment, PPG observations measured from the finger, ear, and forehead
may be analyzed to extract features such as pulse amplitude, pulse width,
and area under the-curve for each cardiac cycle. During certain exemplary
implementations, it was determined that these features are strongly
correlated to stroke volume, and therefore, may provide observable
changes prior to profound decreases in arterial blood pressure that may
to baseline after the removal of the hemodynamic challenge.

[0081] Accordingly, the embodiments of the arrayed, multi-wavelength PPG
sensor 104, such as described herein, may be used to extend these
clinical insights for the early detection of acute hemorrhage and
subsequent circulatory collapse in an emergency, a hospital or a remote
point-of-care environment. Similarly, embodiments of the arrayed PPG
sensor 104 may further be used to make accurate multiple wavelength
measurements that aid in early detection, monitoring and treatment of a
variety of other vascular diseases. These vascular diseases, for example,
include peripheral vascular disease, arterial disease, hemorrhage,
hemodynamic shock, carbon monoxide poisoning, anemia, arterial compliance
and aging, endothelial function, vasospastic conditions such as Raynaud's
phenomenon, microvascular blood flow and tissue viability.

[0082] Use of a disposable, multiple wavelength sensor allows for
non-invasive and continuous monitoring of a patient's physiological
parameters in traditional hospital environments and in extended
environments such as at a site of accident, in an ambulance or in a war
situation, thus saving lives and expediting recovery from injury and
illness. Particularly, the PPG sensor 104 allows for improvements in
general clinical practice by providing easy and immediate access to
patient's total hemoglobin concentration and composition in emergency and
acute care, specifically in the areas of blood transfusion and fluid
management. Accurate total hemoglobin and dyshemoglobin measurements
greatly improve patient safety and quality of care, because the
oxygenation can be assessed and treated immediately in a cost-effective
and user-friendly manner.

[0083] Further, the PPG sensor's continuous monitoring ability may be used
to improve management of bleeding patients by adopting informed blood
transfusion strategies, thus resulting in fewer complications during
surgery and intensive care. Additionally, the risk of arterial
catheterization and infection is mitigated by using the continuously
monitored information. In certain embodiments, use of the portable PPG
sensor 104 allows for immediate diagnosis and treatment of
carbon-monoxide poisoned patients in ambulatory or emergency room
scenarios. In certain other embodiments, the absence of complicated
source-detector rearrangements for multiple wavelength measurements in
the PPG sensor 104 allows for painless hemoglobin and hematocrit tests.

[0084] Embodiments of the monitoring system and methods disclosed
hereinabove, thus, provide a non-invasive, inexpensive and efficient
technique for monitoring and evaluating the physiological parameters, and
in turn the health of a subject. Particularly, the portable nature of the
monitoring system described herein greatly improves medical outcomes by
expanding physiological monitoring to previously "unmonitorable"
settings, for example, in the battlefield. Use of heterogeneous,
co-located multiple wavelength radiation sources and detectors allows
continuous monitoring of a plurality of physiological parameters and
corresponding health conditions, while improving infection control
through the use of a single-patient-use disposable monitoring system.

[0085] Further, the adaptive configuration of the sources and detectors
allows for multiple wavelength measurements that allow extension to
several other clinical applications without causing undue patient
discomfort. In particular, selective operation of the sources and
detectors may be used to optimize the power consumption and ensuring a
desired quality of physiological parameter measurements. Additionally,
the portability of the monitoring system improves accessibility to
medical diagnostic capabilities in remote locations in a cost effective
manner, thus minimizing hospital stay while also allowing automatic
recording, assessing and transmitting vital medical information to a
central/remote healthcare system for storage and evaluation.

[0086] Although specific features of various embodiments of the invention
may be shown in and/or described with respect to some drawings and not in
others, this is for convenience only. It is to be understood that the
described features, structures, and/or characteristics may be combined
and/or used interchangeably in any suitable manner in the various
embodiments, for example, to construct additional assemblies and
techniques.

[0087] While only certain features of the present invention have been
illustrated and described herein, many modifications and changes will
occur to those skilled in the art. It is, therefore, to be understood
that the appended claims are intended to cover all such modifications and
changes as fall within the true spirit of the invention.

Patent applications by Aharon Yakimov, Niskayuna, NY US

Patent applications by Jeffrey Michael Ashe, Gloversville, NY US

Patent applications by Milos Todorovic, Niskayuna, NY US

Patent applications by Siavash Yazdanfar, Niskayuna, NY US

Patent applications by GENERAL ELECTRIC COMPANY

Patent applications in class And other cardiovascular parameters

Patent applications in all subclasses And other cardiovascular parameters